Add back Java resources to apk without Java code.

With commit 33360dd5 we moved Java
resource packaging forward to creation of the jar file. But the Java
resource packaging will be skipped if a module has no Java code at all.
(The build system does support building an apk without Java code.)
In this change we add back the Java resources directly to the built apk
when the apk has no Java code.

Bug: 19947218
Change-Id: I0e1a65a9cbe656974f8ef3923b2f15e9efa5feb9